Combustion apparatus



Jan. 11, 1966 J. E. MCCULLOUGH COMBUSTION APPARATUS Filed Feb. ll, 1963 4 Sheets-Sheet l Atto y Jam 11, 1966 J. E. MCCULLOUGH COMBUSTION APPARATUS 4 Sheets-Sheet 2 Filed Feb. ll, 1963 Fig. 2

INVENTOR,

John E. McCullough /wwl Atto ey 4 Sheets-Sheet 5 Filed Feb. l1 1963 INVENTOR.

John E. McCullough At orney Jan. 11, 1966 J, E MGCULLOUGH 3,228,450

GOMBUSTION APPARATUS Filed Feb. ll 1963 4 Sheets-Sheet 4 REcxRcULATlNG m coMeUsTloN m PRODUCTS |37 5 comausTlON T AIR l --Mr-:Tfman FUEL Q on. 1N

zoNE

INVENTOR.

John E. McCullough Aiforzy United States Patent O 3,228,450 CMBUSTION APPARATUS John E. McCullough, Carlisle, Mass., assigner to Arthur D. Little, Inc., Cambridge, Mass., a corporation of Massachusetts Filed Feb. 11, 1963n Ser. No. 257,645 9 Claims. (Cl. 158-77) This invention relates to combustion devices and more particularly to combustion devices which are suitable for hot Water and residential hea-ting using fuel oil.

There are many different types of oil burners available for residential use. However, the most common type now in use can be described as a high-pressure nozzle burner which produces a line oil spray or mist which is mixed with combustion air and burned. This type of burner has been used successfully for many years, but the design requires periodic maintenance and is not suited for applications requiring oil consumption rates less than about about 0.75 gallon per hour.

The drawbacks in the presently used oil burners indicate the need for a combustion device which is dependable-that is, a burner which is relatively maintenance free. There is also a need for a small oil burner which can operate efciently and dependably at very low oil consumption rates on No. 2 fuel oil. Finally, it is desirable that such a burner be readily adaptible to installations in existing furnace equipment, be of small size, and of quietoperation.

It is therefore a primary object of this invention to provide a novel, dependable, combustion device suitable for being incorporated in residential oil heating systems. It is another object of this invention to provide a combustion device of the character described which is of small size, quiet operation, and exible in its adaptation to present installations in existing oil burner equipment. It is a further object of this invention to -provide such a burner which is able to operate over a range of burning rates and particularly down as -low as 0.1 to 0.3 gallon of No. 2 fuel oil per hour for applications such as oil-tired domestic hot water heaters. Other objects of the invention will in part he obvious and will in part be apparent hereinafter.

The invention accordingly Icomprises the several steps and the relations of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combinations of elements and arrangement of parts which are adapted to eect such steps, all as exempliiied in the following detailed disclosure, and the scope of the invention will be indica-ted in the claims.

In the burner of this invention, the combustion device `comprises a hot circular vaporizing trough into which atomized and partially vaporized oil is hurled by centrifugal force and mixed with air to form a combustible mixture. This mixture is then available for ignition by a standard high-voltage spark system. When the com-` bastion zone is partially enclosed by this same hot surface as in the case of the combustion device of this invention, the circular vaporizing trough is able to sustain its temperature after ignition without the addition of external heat.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawings in which FIG. l is a longitudinal cross-sectional view of one embodiment of an oil burner constructed in accordance with this invention;

FIG. 2 is a cross-section of the burner lof FIG. 'l along line 22;

3,228,450 Patented Jan. 11, 1966 'ice FIGS. 3-5 are fragmentary cross-sections of the circular vaporizing trough showing various ways of incorporating heating means.

FIG. 6 is a top plan view of a modification of the atomizin g disk;

FIG. 7 is another embodiment, in longitudinal crosssection, of the oil burner of this invention;

FIG. 7a is an end view of the burner of FIG. 7 showing the air inlet ports;

FIG. 8 is a cross-sectional View of the appara-tus of FIG. 7 taken along line 3 8;

FIG. 9 is a cross-sectional view of the apparatus of FIG. 7 taken along line 9 9; and

FIG. 10 is a simplified cross-sectional view of the combustion chamber of this invention showing in part the fluid lio-w paths of the fuel oil, air and products of combustion.

The combustion device of this invention may be generally described as comprising, in combination, a circular vaporizing trough formed as a shallow cylinder, one end having an inwardly inclined rim andthe other an end plate with a centrally-positioned circular aperture; a foraminous disk located within the vaporizing trough and having a radius somewhat less than the inner radius of the cylinder; a shaft adapted to support and rotate the disk extending through the aperture in the end plate and defining therewith an annular fluid passage into the vaporizing trough; means to deliver fuel oil through the shaft to the central porti-on of the rotating disk; a heater to heat the outer Wall of the cylinder; and suitable electrodes to provide an ignition spark for starting. Several embodiments of this combustion device are illustrated and its incorporation into a fuel oil burner described.

Combustion of fuel oil is achieved by a method cornprising the steps of directing a stream of fuel oil onto the central port-ion of a foraminous disk, rotating the disk at a speed sufficient to force the oil to the periphery of the disk and hurl it olf through centrifugal force to atomize and vaporize at least a portion of the fuel cil; and directing the resulting atomized and vaporized oil against a hot impervious surface thereby to achieve combustion with air delivered to the combustion region.

FIGS. 1 and 2 illustrate one embodiment of the burner of this invention. It should be noted that, although the combustion device and burner of FIGS. l, 7 and 10 are illustrated in a horizontal position for convenience of presentation and comparison, such positioning is not essential. The apparatus may, in fact, be oriented in any position desired; and hence in the following description such terms as forward, afterj upper and lower are used only as convenient terminology.

The burner in FIGS. l and 2 is generali-ly indicated by numeral 1G while the combustion device is generally indicated by numeral 11. Turning lirst to the combustion device, it will be seen that it comprises a circular Vaporizing trough 15 which is defined by a back wall 16, a circular side wall i7, and an inclined forward wall 18. The back wall 16 of the vaporizing trough 15 is joined to a conica-ily shaped combustion air chamber Ztl and at their juncture there is a combustion air inlet port 21. The entire vaporizing trough 15 is formed of a metal which' is impervious to gas ow and is capable of withstanding the high temperature required for proper operation of the combustion device. This, it should be noted, is in direct contrast to combustion devices employing gas-porous ceramics and cooled chamber walls. 1

A metal sheath heating element 22 substantially surrounds the side wall 17 of the circular vaporizing trough and is in thermal contact with it. Through conduction the inner wall 23 of the circular vaporizing trough is heated by this heating element during starting only. Subs'equently the Wall is maintained at the required high ternperature by the combustion process. The heating element 22 need not be of the cross-sectional shape shown in FIG. 2. It may be of any suitable configuration, such as circular in cross-section as shown in FIG. 3. In the use of such a heating element it is preferable to thermally bond it to wall 17 through the use of a suitable heat conducting material such as thermal cement 24. The heating element may also be integral with one wall forming the circular vaporizing trough 15, or be a part of a wall. As'an example, the heating element 12 in FIG. 4 is joined at 13 to walls 16 and 18 and takes the place of wall 17. In FIG. it will be seen that the heating element 14 serves as a portion of wall 16. Thus it will be seen that any heating means which is capable of initially heating the metal circular vaporizing trough is suitable and many combinations of heaters and walls may be used.

Within the circular vaporizing trough 15, an atomizing disk 25- is rotated at medium to high speeds. The disk 25 is held in place by disk mount 26 and a retaining member 27 which are joined through the atomizing disk 25 by suitable means such as screws 23. The radius of this disk should preferably be as great as possible, that is only slightly less than the inner radius of the shallow cylindrical portion defined by walls 17 of the vaporizing trough. The disk should, of course, be of such size that it clears the internal wall 23 and the electrode 40 and 41 if they extend deeply into the trough as shown in FIG. 2. Th-is rotating disk 25 may be further characterized as a flat, planar element, without any radial fins or extremities which create turbulence.

The disk, shown as a screen in FIGS. l and 2, is rotated by shaft 29 which is hollow and which contains a second hollow shaft 30. Within the second hollow shaft 30 is located an oil feed tube 31 which is mounted in rotating shaft 29 through suitable bearing 32. At the end of oil feed tube 31 and rotating shaft 29 there is an oil delivery zone 33, one side of which is defined by that portion of the screen 34 which is exposed to the oil delivery zonet Where the atomizing disk 25 passes between the disk mount 2,6 and retaining member 27, there is provided a passageway 35 by virtue of the open screen construction. This passageway is sutiicient to permit oil delivered to the oil delivery zone 33 to be forced out centrifugally over the entire surface of the atomizing disk 25 and out to its periphery.

For ignition there are provided electrodes 40 and 41 which are placed between the gap 42 which is dened by the spacing left in the heating element 22 as is seen in FIG. 2,. Other ignition means are also suitable and these include resistance heaters, glowing coils and gas pilots, Terminals 44 provide, through shielded cables 45, suitable connections between the heating element 22 and an electrical source. This circuitry also includes a switch 46` which may be automatic (thermostat) or manual to start the ow of electrical current to the heating element. In like manner terminals 48 (only one of which is shown) are connected to electrodes 40 and 41 which are in turn partially encased in insulating members 49. Associated with the circular vaporizing trough and the heat-ing element 22 and in thermal contact therewith is a thermal switch 53 (FIG. 2) which is connected to a thermal switch terminal 54. This thermal switch is used to actuate the various elements of the combustion chamber as explained below. The switch is connected to the heating element terminal through relay 55, to the electrode terminal 48 through switch 57 and transformer 58, to the motor 70 driving the fan and the atomizing disk, and' to the oil pump 61.

FIG. 6 illustrates an alternative configuration of the Aatomizing disk. In place of a screen, the atomizing disk 62 of FIG. 6 comprises a plurality of radial wires 63. The radial wire atomizing disk of FIG. 6 is mounted in the same manner as the screen atomizing disk of FIGS. 1 and 2. In this-type of mounting a passageway 35 between disk mount 26 and retaining member 27 is fu-rnished by the spacings between the vradial wires 63 and in rotating the disk the oil is hurled out on the wire surfaces and between the wires in the same fashion it is thrown out on and between the wires making up the atomizing screen disk 25.

Fr-om the above description of the atomizing disk and the two embodiments illustrated, it can be seen that the purpose of the disk is to deliver fuel to the hot inner walls of the vaporizing trough. The rotating foraminous disks described have been found to be particularly well suited for this purpose. However, otherl means adapted to distribute fuel oil within the vaporizing trough may also be used. For example, a stationary hub or other device suitable for ejecting fuel oil toward or against the walls may be substituted for the rotating screen disk of FIG. 1 or the rotating radial wire disk of FIG. 6.

The burner of FIG. 1 is provided with a housing comprising a main cylindrical section 65, a forward conical section 66, and an end plate 67 which is equipped with adjustable air inlet ports not shown. Within the main cylindrical section 65 is located a shaded pole motor 70, which is supported in the main housing 65 by supports 72. The motor 70 is joined to the rotating shafts through bearing 73. There is also provided in the main cylindrical section 65 a four-bladed propeller fan 76 which is mounted on shaft '77 connected to motor 70 through bearing 78. An oil input line 80 brings oil from the oil source, not shown, into the burner and down through the rotating shafts 29 and 30 through the oil feed tube 31. This assembly is joined through a rotary oil seal 81.

FIG. 7 illustrates another embodiment of the apparatus of this invention and -in particular shows the use of a radial vane combustion air fan, in place of the propeller blade fans, located forward of the motor rather than after it as in the case of the apparatus in FIG. 1. In FIGS. 1 and 7 like reference numbers refer to like elements. The combustion device and burner of FIG. 7 are provided with similar circuitry (not shown) for controlling the heater, electrodes, motor, fan and oil pumps as shown in FIG. 1.

In the apparatus of FIG. 7 the rotating atomizing disk 25, is joined by means of the retaining mem-ber 27 to an extension of the rotating shaft 91. Within 91 is an inner sha-ft 92 which is somewhat shorter than that illustrated in the apparatus of FIG. 1. The oil feed tube 31 extends slightly beyond the inner shaft 92, but defines -wit'hin hollow shaft 91 an oil discharge chamber 93 which serves the same purpose as oil delivery zone 33 of the burner of FIG. 1. As in the case of the apparatus in FIG. 1I the oil in the oil discharge chamber 93 is fed against the surface. 34 of the rotating atomizing disk 25 and is forced radially outward through the space between the retaining mem-ber 27 and the shaft extension 90. Thus the oil is transported to the periphery of the atomizing disk 25 through centrifugal force. i

Shaft 91 is mounted in main bearing 94 and is driven by motor 97. This main rotating shaft 92, is mounted in a shaft support (FIG. 8) where is formed of an outer annular ring 98, an inner annular ring 99, and arms V which join the two annular ring supports. The arms 100 define 'between them ports 101 through which combustion air is permitted to enter the burner and flow around motor 97. To support shaft 92 there is also provided bearings 102; and the shaft is driven by motor 97. In order to prevent the -motor 97 from rotating, an anchor arm 107 is fixed to the motor and anchored in an opening 108 in one of the arms 100.

Forward of the motor, the main bearing 94 is mounted in a conical inner support 110 which in turn is joined to an outer support 111 by arms 112 (see. FIG. 9). These arms 112 define between them combustion air inlet ports 113. Outer support 111 is equipped with a right` angle extension 114, which is joined to annular plate 115. The annular plate in turn has attached to it and integral with it three ring extensions 116, 117 and 118. Between the annular plate 115 and the right angle extension 114, there is dened a turbulent air zone 120. Located within this zone 120, is a radial vane combustion air fan 125. Adiacent to the combustion air fan 125 is a diffuser 127 which directs air for combustion from zone 120 to zone 128 and through the annular air inlet passage 129, defined by the edge of walls 16 and shaft 91. The diffuser 127 imparts to the air a high swirl velocity as it enters the vaporizing trough 15 through passage 129.

Around the burner of FIG. 7 there is provided a suit able housing which in the embodiment illustrated comprises a main housing 132 which defines Within it an air inlet zone 133 around the motor 97. The main housing 132 terminates at its forward end in a right angle extension corresponding to and surrounding the right angle extension 114 of the outer support 111. Around the combustion chamber the housing comprises an inner housing cylindrical portion 135, an inclined portion 136, and a cylindrical extension 137 of the inner housing to enclose the combustion zone. The inner housing 135 is attached to the annular ring extension 117 of annular plate 115. Annular extension 116, in turn, is attached to the vaporizing chamber 15, while annular ring extension 118 and the right angle extension 134 of the housing form a means for joining an outer combustion chamber housing 138 which is designed to shield within it the electrode terminals 49 as Well as the heating element terminals 44. To complete the housing there is provided an end plate 140 which has adjustable ports for adjusting the quantity of air introduced into the burner. Such ports 141 are illustrated in FIG. 7a. They have radially moving vanes 142 to control the size of ports 141 and hence the air ow into the burner.

FIG. l0 is provided to diagrammatically indicate the iiow paths of the fuel and the incoming air as well as the combustion zone which exists Within the combustion device of this invention. It will be seen from this figure that effective use is made of all of the volume of the combustion device and that the combustion zone is so designed that its size and extent may be readily controlled. The combustion device of FIG. (which is that of FIG. 1 in the housing of FIG. 7) may be separated from the fan and oil pump and their attendant controls and housing if means are provided to furnish combustion air with a high swirl velocity as illustrated in FIG. 10. Such separation may be required or desired under some conditions of restricted space.

The operation of the burner of this invention may be described using the embodiment of FIG. 1 as an example. Metered oil is supplied through oil input line 80 into the oil feed tube 31 Within the central portion of the shaft 29 which rotates the atomizing disk 25. The metered oil flows into the oil delivery zone 33 and is collected upon face 34 of the atomizing screen disk 25. The centrifugal force developed in the rotation of the disk 25 forces the oil out through the small passageways 35 over the surface of the rotating disk (whether it is a screen or a series of radially extending wires) to the periphery of the disk. By the time the oil reaches the periphery of the disk it is partially vapor-ized and is hurled as a tine mist against the walls of the circular vaporizing trough 15. In the meantime, of course, the -fan is forcing combustion air through the combustion air inlet port 21 to be mixed with the vaporized fuel.

In starting the burner electrical power (for example 110 volts) is applied to the resistance heating element 22 (which characteristically may be a 50G-watt electric range type heating element). The tiow of electrical current to the element is automatically or manually started Iby an actuating switch. When the temperature of the vaporizer trough reaches about 500 F., the thermal switch 53 actuates relay 55 which turns off the electrical heater, actuates motor 70 which drives the atomizing disk 25 and fan 76, starts the oil metering pump 61, and energizes the ignition transformer S8 through switch 57, thus energizing electrodes 40 and 41. As the fuel oil flows along the wires of the atomizing disk 2S, the oil iilm remains intact since no hot combustion gases are present during the starting period to cause vaporization. Small droplets are formed at the ends of the wires and impinge on the heated circular vaporizing trough. Thus the oil droplets vaporize and the vapor-air mixture within the trough is ignited. with the electrical spark created across electrodes 40 and 41. Combustion is immediately established after which the ignition transformer 58 is de-energized by switch 57 which is controlled by the fact that it is immersed in the exhaust products. After about 60 seconds the combustion chamber walls, i.e., 16, 17 and 18, are at the operating temmrature of about 800 F. It will be appreciated at this point that neither the heating element 22 or the electrode 40 are functioning and that combustion is self-sustaining. Once initial ignition is achieved by a spark from the electrodes and steady-state operation conditions attained, a portion of the oil is vaporized as it is transported outwardly over the now hot rotating disk. Thus the fuel oil leaves the disk partially vaporized and partially atomized. The hot combustion gases swirling around the rotating disk also provide some of the energy required for vaporization which means that not all of the heat of vaporization must be derived from the trough walls.

The burner is shut off by first stopping the fuel oil metering pump or {le-energizing a suitable solenoid valve. The combustion air fan continues to operate until the thermal switch 53 attached to the circular vaporizer through 15 opens the circuit, that is, when this switch has reached a temperature of about 500 F. At this temperature both the atomizing disk 25 and the fan 76 are stopped by virtue of the fact that the relay 55 opens and disconnects motor '70.

Since the circular vaporizer trough walls and ignition electrodes reach temperatures in excess of 800 F. and operate in an are-a of high turbulence, no significant carbon deposit is formed on these surfaces. Combustion is eicient with 11 to 13% CO2 and zero smoke on the Bachrach scale. This is a significant advantage of this combustion device since No. 2 fuel oil normally leaves a residue. For this reason, burners which utilize the vaporization of fuel at low temperatures with cool porous combustion surfaces are not suitable for buring No. 2 fuel oil.

The unique combustion device employed in the burner of this invention makes it possible to operate on extremely low fuel oil feed rates. Complete and eicient combustion has been obtained with burning rates as low as 0.1 gallon 1per hour of No. 2 fuel oil. This in turn means that the burner may be made small enough to employ in domestic hot water heaters. Moreover, the operation of the burner is flexible enough to operate at burning rates up to 1.5 gallons and more per hour, making the burner of this invention suitable for installation in existing furnace equipment for domestic heating.

From the above description of the burner and particularly the combustion device of this invention it will be seen that there is provided an oil burner which is efficient, dependable, able to operate over a wide burning rate range, and exible in size. Moreover, it has been found in actual operation that the burner is quiet to run and that it is readily adaptable to installation in existing furnace equipment.

It will thus he seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and since certain changes may be made in carrying out the above method and in the construction set forth Without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim: 1. A combustion device, comprising in combination (a) a fluid-impermeable circular vvaporizing trough means formed of a back wall,v a circular side -wall and an inclined forward wall, having a combustion air inlet and a combustion products outlet, and defining within it at lea-st a portion 'of the combustion zone;

(b) a rotating forarninous disk, formed of spaced metal wire and shaped in the configuration of a flat planar element, located within said circular vaporizing trough means and adapted to deliver atomized fuel oil toward the internal surface of said trough means;

(c) -fuel delivery means arranged to supply fuel oil to the central portion of said disk;

(d) heating means in thermal contact with at leastv one of said walls forming said trough means;

(e) ignition means positioned within said trough means for initially igniting said fuel oil within said trough means; and l (f) means for supplying combustion air to said trough means through said combustion air inlet.

2. A combustion device in accordance with claim 1 wherein said foraminous disk is a metal screen.

3. A combustion device in accordance with claim 1 wherein said foraminous disk is formed of a plurality of radially extending metallic wires.

4. A combustion device in accordance with claim 1 including switch means in thermal contact with said vaporizing trough means and said heating means and adapted to control said heating means and said ignition means.

5. A combustion device in accordance with claim 1 wherein said heating means comprises at leastv a portion of at least one of said Walls of said trough means.

6. A combustion device in accordance with claim l including housing means surrounding said vaporizing trough means, said ignition means and said heating means and adapted to direct combustion air -int-o said combustion air inlet and products of combustion -from said vaporizing trough means.

7. A fuel oil burner, comprising in combination (a) a uid-impermeable circular vaporizing trough means formed of a back wall, a circular side wall and an inclined forward wall, having a combustion air inlet and combustion products outlet, and defining within it at least a portion of the combustion zone;

(b) a rotating foraminous disk, formed of spaced metal wire and shaped in the configuration of a flat planar element, located within said circular vaporizing trough means and adapted to deliver atomized fuel oil toward the internal surface of said trough means;

(c) fuel delivery means arranged to supply fuel oil to the central portion of said disk;

(d) fan means for supplying air to said trough means through said combustion air inlet;

(e) heating means in thermal contact with at least one 'of said Walls forming said trough means;

(f) ignition means positioned within said trough means for initially igniting said fuel oil within said trough means;

f (g) switch means in thermal Contact with said vaporizing trough means and adapted to c-ontrol said heating means and said ignition means; and

(h) a housing enclosing said burner and including means for regulating the intake of combustion air and means for directing hot combustion products at planar element, located wtithin said circularl vaporizing trough means andl adapted to deliver atomized fuel oil toward the internal surface of said trough means;

(c) shaft means adapted to support and rotate said disk and extending through said combustion -air inlet and defining with said inlet an annular fluid passage into said vaporizing trough means;

(d) means internal of said shaft means for delivering liquid fuel to the central portion of said disk;

(e) fan means for supplying combustion air to said annular fluid passage;

(f) driving means adapted to rotate said shaft and said Ifan;

(g) heating means in thermal contact with at least one `of said walls forming said trough means;

(h) ignition means positioned Within said trough means for initially igniting said fuel oil within said trough means;

(i) switch means in thermal contact with said Vaporizing trough means and adapted to control saidv driving, heating and' ignition means; and

(j) a housing enclosing said burner and including means forregulating the intake of combustion air.

9. A fuel c-il burner in accordance with claim S including diffuser means associated with said fan means and adapted to impart a high swirl velocity tov said combustion air prior to combustion.

References Cited. by the Examiner UNITED STATES PATENTS Re.19,766 11/1935 Powers 15s-4 1,327,256 1/1920 Scheminger 158-77 1,692,617 11/1928 Bowen -g 239-223 1,707,774 l 4/1929 Scheminger 158-77 1,846,978 2/1932 Parker 15S-117.5 1,893,902 1/1933 Meachem 15S-117.5 1,977,798 12/1934 Korth 158-4 2,126,959 8/1938 Heuer 158-77 2,507,006 5/ 1950 Hammell et al. 158-77 2,568,763 9/1951 Ray 158-77 FOREIGN PATENTS 953,455 11/1956 Germany.

FREDERICK L. MATTESON, IVR., Primary Examiner.

MEYER PERLIN, JAMES W. WESTHAVER,

- Examiners. 

1. A COMBUSTION DEVICE, COMPRISING IN COMBINATION (A) A FLUID-IMPERMEABLE CIRCULAR VAPORIZING TROUGH MEANS FORMED OF A BACK WALL, A CIRCULAR SIDE WALL AND AN INCLINED FORWARD WALL, HAVING A COMBUSTION AIR INLET AND A COMBUSTION PRODUCTS OUTLET, AND DEFINING WITHIN IT AT LEAST A PORTION OF COMBUSTION ZONE; (B) A ROTATING FORAMINOUS DISK, FORMED OF SPACED METAL WIRE AND SHAPED IN THE CONFIGURATION OF A FLAT PLANAR ELEMENT, LOCATED WITHIN SAID CIRCULAR VAPORIZING TROUGH MEANS AND ADAPTED TO DELIVER ATOMIZED FUEL OIL TOWARD THE INTERNAL SURFACE OF SAID TROUGH MEANS; (C) FUEL DELIVERY MEANS ARRANGED TO SUPPLY FUEL OIL TO THE CENTRAL PORTION OF SAID DISK; (D) HEATING MEANS IN THERMAL CONTACT WITH AT LEAST ONE OF SAID WALLS FORMING SAID TROUGH MEANS; (E) IGNITION MEANS POSITIONED WITHIN SAID TROUGH MEANS FOR INITIALLY IGNITING SAID FUEL OIL WITHIN SAID TROUGH MEANS; AND (F) MEANS FOR SUPPLYING COMBUSTION AIR TO SAID TROUGH MEANS THROUGH SAID COMBUSTION AIR INLET. 